Method for checking whether a mobile station supports a location service (LCS) in a packet switched mode

ABSTRACT

The present invention is related to LoCation Services (LCS) in General Packet Radio Service (GPRS). Because the specification of LCS was missing in the first versions of the technical specifications of GPRS, but already introduced in the GSM specifications, there will be a number of MSs having LCS capabilities when attached to circuit switched serving nodes (MSCs) but not when attached to packet switched serving nodes (SGSNs). When a location request for one such MS attached to both an MSC and an SGSN is directed to the SGSN first, an error may occur. The present invention discloses a method solving this problem by informing the associated HLR if the MS supports location service in packet switched mode or not at the time the MS attaches the network. The information is stored in the HLR, and when the location service node in the network receives a location request for that MS, the location node invokes the HLR for the information. If the MS does not support location service in packet switched mode, the HLR informs the location service node to firstly request the MS attached MSC for the location of the MS.

FIELD OF THE INVENTION

The present invention is related to LoCation Services (LCS) in GeneralPacket Radio Service (GPRS). Terminology and abbreviations within thetechnical field of GPRS, well known for persons skilled in the art, willbe used in this application, and reference is made to the 3GPP TS 23.271specification for a detailed description of LCS.

BACKGROUND OF THE INVENTION

Higher data speed in cellular phone systems allows offering of new typesof services. One of the service types that is expected to have abreakthrough with the launch of GPRS is the Localization Services. Theseare services providing mobile telephone users with information aboutwhere objects or persons are localized. This information may bepresented on the user terminal on e.g. a digital map, or simply throughstatement of position, address or place name.

Further, Location Services may be considered as a network providedenabling technology consisting of standardised service capabilities,which enable the provision of location applications. The main componentin LCS is the GMLC (Gateway Mobile Location Centre), to which alllocation requests are transmitted, providing the requested location fromthe mobile network. The application(s) may be service provider specific,for example tracking of persons or vehicles. However, the description ofthe numerous and varied possible location applications that are enabledby this technology are outside the scope of the present document.

As mentioned above, LSC will probably not become common in the GSMenvironment before the launch of GPRS. However, LSC was specified forGSM already in GSM 03.71, Release 4, but not in originally for GPRS. LSCwas introduced in GPRS as late as in the 3GPP TS 23.271 released in2001.

As a result of this, a large number of GPRS/GSM MSs will support LSC forGSM, but not for GPRS. This applies for MSs that have already beenmanufactured and for those being manufactured in the near future.Consequently, there will exist a large number of MSs with inconsequentLCS capabilities in many years ahead.

The problem then occurs when an LCS Client (another MS, a service nodeetc.) wants to track the position of a Mobile Station (MS) via GPRS,i.e. via an SGSN node, and that MS does not support LCS Capability forGPRS.

Due to that LCS for GPRS is standardised in a later release of thestandard than LCS for GSM and even later than GPRS itself, it isentirely possible (even likely) to have MSs that support both LCS forGSM and GPRS, but does not support LCS for GPRS.

In this case, if the request for positioning is initially sent to theSGSN node, the positioning may fail in SGSN if the MS does not supportLCS for GPRS, whereas if the request had been sent to MSC node (circuitswitched GSM), it would have been successful.

The only known solution today is that the SGSN returns an error message,and that the GMLC due to this retransmits the location request towardsthe MSC.

The problem with the solution as described above is that the fetching ofthe positioning might be time critical, meaning that the response willbe returned to the LCS Client too late if we first have to try againstSGSN and then perform a second try against MSC.

SUMMARY OF THE INVENTION

The main object of the present invention is to overcome theabove-identified problems. The present invention discloses a method andapparatus for providing location service to a mobile station within acellular network wherein said mobile station is able to operate in botha packet switched and a circuit switched mode, and wherein said mobilestation is attached to a first serving node within said cellular networkwhen operating in the packet switched mode and attached to a secondserving node within said cellular network when operating in the circuitswitched mode, wherein the present invention, in response to said mobilestation attaching to the first service node, determining whether saidmobile station supports the location service in packet switched mode andstoring said determination in said cellular network. Further inaccordance with the present invention, in response to receiving alocation request for said mobile station from a location node whereinsaid mobile station is currently being served by a particular servicenode within said cellular network, determining the address of theserving node and further determining whether the mobile station supportsthe location service in packet switched mode. In response to adetermination that the mobile station does not support the locationservice in packet switched mode, the present invention further informingsaid location node that the location request should be directed to saidsecond serving node.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overview of the nodes involved in a Location Request andthe interaction them between,

FIG. 2 shows an example of the message sequence of an attach procedureaccording to the 3GGP TS 23.060 specification,

FIG. 3 shows an example of the message sequence of a mobile terminatedlocation request according to the 3GGP TS 23.271 specification,

DETAILED DESCRIPTION

The present invention discloses a method to inform the Home LocationRegister (HLR) in a GPRS/GSM network about the LCS Capabilities of theattached MS. When Gateway Mobile Location Centre (GMLC) then invokes theHLR for routing information (i.e. SGSN and/or MSC address), the HLR willbased on the information from SGSN be able to tell GMLC whether itshould try SGSN or MSC first, and by that having a larger likelihood tosucceed with the positioning attempt of the subscriber.

The attached figures show the interactions between the different nodesinvolved in the Location Request.

According to the present invention, when an MS performs a GPRS Attachtowards SGSN, it will inform the SGSN about the LCS capabilities itsupports for GPRS network. When the MS roams into another SGSN, the LCSCapability information will also be informed to the new SGSN.

During the Attach or Inter SGSN Routing Area Update procedures the SGSNwill update HLR about the MS's new location. According to the presentinvention, the SGSN shall then in addition include the LCS Capabilityinformation for this MS in the signalling procedure against HLR.

The HLR will now be informed about the LCS Capabilities for thissubscriber, and can then use this information later on when apositioning is to be performed for this subscriber.

Consider that an LCS Client now wants to provide the position of thissubscriber:

-   -   1) The LCS Client sends the Location Request towards the GMLC.    -   2) GMLC interrogates HLR for retrieval of routing information.        The HLR will return routing information for SGSN or MSC or both,        depending on where the subscriber is attached (GPRS Attached or        IMSI Attached or both). As the HLR today only knows that the        subscriber has attached to an SGSN and/or MSC, there is no valid        information to prioritise the possibilities for a successful        positioning on either SGSN or MSC in the cases when the        subscriber is attached to both domains. However, when the        feature of the present invention is supported, the HLR will,        based on the information concerning the MS's Capabilities for        LCS, be able to inform the GMLC if it should try the SGSN or the        MSC first. HLR should then, for the subscribers where SGSN have        indicated that LCS for GPRS is not supported, still return both        SGSN and MSC address, but indicate that the MSC is the preferred        one.    -   3) GMLC will then send the Location Request to the MSC. MSC then        starts the location procedure against the MS and preferably gets        the position, which then is returned via GMLC back to the LCS        Client.

The sequence in FIG. 2 shows an example of the Attach procedure, asdescribed in the 3GPP TS 23.060 specification. In the following, thesequence adjusted according to the present invention will be described.

-   -   1) For GPRS, the MS initiates the attach procedure by the        transmission of an Attach Request message to the SGSN. The        message contains among others the MS's GPRS LCS capabilities. In        this example the MS does not support any LCS Capabilities for        GPRS.    -   2) If the SGSN number has changed since the GPRS detach, or if        it is the very first attach, then the SGSN informs the HLR:        -   a) The SGSN sends an Update Location to the HLR. The            information that the MS does not support LCS for GPRS is            included.        -   b) The HLR acknowledges the Update Location message by            sending an Update Location Ack to the SGSN.    -   3) The SGSN sends an Attach Accept message to the MS.

The sequence in FIG. 3 shows an example of a Mobile Terminated LocationRequest (MT-LR) procedure, as described in the 3GPP TS 23.271specification. In the following, the procedure adjusted according to thepresent invention will be described.

-   -   1) An external LCS client requests the current location of a        target UE from a GMLC.    -   2) GMLC sends a SEND_ROUTING_INFO_FOR_LCS message to the home        HLR/HSS of the target UE to be located with the IMSI, PDP        address or MSISDN of this UE as input parameters.    -   3) The HLR/HSS then returns one or several of the addresses, the        current SGSN and/or MSC and whichever of the IMSI and MSISDN        that was not provided in step (2) for the particular UE. Note        that HLR may prioritise between the MSC or SGSN address sent to        GMLC. This priority criterion is based on the present invention,        and by that, HLR will in this example prioritise the MSC        address.    -   4) In case GMLC receives only the MSC address, the MT LR        proceeds as the CS-MT-LR procedure against MSC. In case GMLC        receives only the SGSN address, the MT LR proceeds as the        PS-MT-LR procedure against SGSN. In case the GMLC receives        several of the following addresses, SGSN and/or MSC, it has to        decide where to send the location request. According to the        present invention, the decision will be based on the        prioritisation made by HLR, and in this example GMLC will        therefore request the MSC first.    -   5) When the location of the subscriber is returned from MSC the        GMLC sends the location service response to the LCS client.

The main advantage with the present invention is that since the HLR willbe able to make a proper prioritisation between the different possiblerouting information addresses for a location request, and not justrandomly as today, the GMLC will be able to select the one having alarger likelihood for a successful location request. For time criticallocation requests, this might be the difference between an acceptableand an unacceptable response seen from the LCS Client point of view.

The present invention is also applicable to circuit switched corenetworks in GSM systems, and core networks.

1. Method for a location service provided by a location node in acellular network wherein Mobile Stations (MSs) are being able to operatein both a packet switched and a circuit switched mode, the MSs areattached to a first serving node for the packet switched mode, and to asecond serving node for the circuit switched mode, the cellular networkincludes a register containing information concerning the location ofthe MSs, comprising the steps of: a) in the event one of the MSsattaches to the first serving node, informing the register whether theMS supports the location service in packet switched mode, or in theevent one of the MSs attaches to the second serving node, informing theregister whether the MS supports the location service in circuitswitched mode; and b) when a location request for the MS is received atthe location node, requesting the register for serving node address, andfurther determining whether the MS supports the location service inpacket switched mode; in response to a determination that the MS doesnot support the location service in packet switched mode, informing thelocation node that the location request shall be directed to the secondserving node.
 2. Method according to claim 1, wherein that the cellularnetwork is a GSM/GPRS network, the first serving node is an SGSN, thesecond serving node is an MSC and the register is an HLR.
 3. Methodaccording to claim 2, wherein that the location service is the locationservice defined in the 3GPP TS 23.271 specification, and the locationnode is a GMLC.
 4. Method according to claim 2 wherein step b), therequest to the register for the serving node address is a Send RoutingInfo for LCS message, and the information regarding that the locationrequest shall be directed to the second serving node is included in aSend Routing Info for LCS acknowledge.
 5. Method according to claim 1wherein that in step a), the information whether or not the MS supportsthe location service in packet switched mode is included in an AttachedRequest message transmitted from MS to the SGSN and in an UpdateLocation message transmitted from the SGSN to the HLR.
 6. A cellularnetwork including a location node for providing a location servicewherein Mobile Stations (MSs) are being able to operate in both a packetswitched and a circuit switched mode, wherein the MSs are attached to afirst serving node for the packet switched mode, and to a second servingnode for the circuit switched mode, the cellular network includes aregister containing information concerning the location of the MSs,comprising: a) in the event one of the MSs attaches to the first servingnode, means for informing the register whether the MS supports thelocation service in packet switched mode, or in the event one of the MSsattaches to the second serving node, means for informing the registerwhether the MS supports the location service in circuit switched mode;b) when a location request for the MS is received at the location node,means for receiving a request for serving node address, and said meansfurther determining whether the MS supports the location service inpacket switched mode by evaluating information provided by saidregister; and in response to a determination that the MS does notsupport the location service in packet switched mode, means forinforming the location node that the location request shall be directedto the second serving node.
 7. The network according to claim 6, whereinthat the cellular network is a GSM/GPRS network, the first serving nodeis an SGSN, the second serving node is an MSC and the register is anHLR.
 8. The network according to claim 7, wherein that the locationservice is the location service defined in the 3GPP TS 23.271specification, and the location node is a GMLC.
 9. The network accordingto claim 6 wherein said information whether or not the MS supports thelocation service in packet switched mode is included in an AttachedRequest message transmitted from MS to the SGSN and in an UpdateLocation message transmitted from the SGSN to the HLR.
 10. The networkaccording to claim 6 wherein said means for requesting to the registerfor the serving node address uses a Send Routing Info for LCS message,and the information regarding that the location request shall bedirected to the second serving node is included in a Send Routing Infofor LCS acknowledge.
 11. A method for providing location service to amobile station within a cellular network wherein said mobile station isable to operate in both a packet switched and a circuit switched mode,and wherein said mobile station is attached to a first serving nodewithin said cellular network when operating in the packet switched modeand attached to a second serving node within said cellular network whenoperating in the circuit switched mode, comprising the steps of: Inresponse to said mobile station attaching to the first service node,determining whether said mobile station supports the location service inpacket switched mode and storing said determination in said cellularnetwork; In response to receiving a location request for said mobilestation from a location node wherein said mobile station is currentlybeing served by a particular service node within said cellular network,determining the address of the serving node and further determiningwhether the mobile station supports the location service in packetswitched mode; In response to a determination that the mobile stationdoes not support the location service in packet switched mode, informingsaid location node that the location request should be directed to saidsecond serving node.
 12. The method of claim 11 further comprising thestep of, in response to said mobile station attaching to the secondservice node, determining whether said mobile station supports thelocation service in circuit switched mode and storing said determinationin said cellular network.
 13. The method of claim 11 wherein saidstoring of said determination is performed by a home location register(HLR) associated with said mobile station.
 14. The method of claim 11wherein said first service node is an SGSN and said second serving nodeis an MSC.
 15. The method of claim 14 wherein said step of determiningwhether said mobile station supports the location service in packetswitched mode is performed by evaluating an Attached Request messagetransmitted from said mobile station to the SGSN and in an UpdateLocation message transmitted from the SGSN to a home location register(HLR) associated with the mobile station.
 16. The method of claim 14wherein said location request for said mobile station is a Send RoutingInfo for LCS message and the information and said step of informing saidlocation node that the location request should be directed to saidsecond serving node includes a Send Routing Info for LCS acknowledge.17. The method of claim 11 wherein said location service is the locationservice defined in the 3GPP TS 23.271 specification and said locationnode is a GMLC.
 18. A system for providing location service to a mobilestation within a cellular network wherein said mobile station is able tooperate in both a packet switched and a circuit switched mode, andwherein said mobile station is attached to a first serving node withinsaid cellular network when operating in the packet switched mode andattached to a second serving node within said cellular network whenoperating in the circuit switched mode, comprising: In response to saidmobile station attaching to the first service node, means fordetermining whether said mobile station supports the location service inpacket switched mode and storing said determination in said cellularnetwork; In response to receiving a location request for said mobilestation from a location node wherein said mobile station is currentlybeing served by a particular service node within said cellular network,means for determining the address of the serving node and furtherdetermining whether the mobile station supports the location service inpacket switched mode; In response to a determination that the mobilestation does not support the location service in packet switched mode,mans for informing said location node that the location request shouldbe directed to said second serving node.
 19. The system of claim 18further comprising, in response to said mobile station attaching to thesecond service node, means for determining whether said mobile stationsupports the location service in circuit switched mode and storing saiddetermination in said cellular network.
 20. The system of claim 18wherein said means for storing of said determination includes a homelocation register (HLR) associated with said mobile station.
 21. Thesystem of claim 18 wherein said first service node is an SGSN and saidsecond serving node is an MSC.